[webkit-changes] [WebKit/WebKit] 470bd5: Use mapped files in CacheStorageDiskStore

[bnham]

  Branch: refs/heads/main
  Home:   https://github.com/WebKit/WebKit
  Commit: 470bd54de983712380aa5478840b0fe53e566f76
      https://github.com/WebKit/WebKit/commit/470bd54de983712380aa5478840b0fe53e566f76
  Author: Ben Nham <nham at apple.com>
  Date:   2023-07-20 (Thu, 20 Jul 2023)

  Changed paths:
    M Source/WTF/wtf/FileSystem.h
    M Source/WebKit/NetworkProcess/storage/CacheStorageDiskStore.cpp
    M Source/WebKit/NetworkProcess/storage/CacheStorageDiskStore.h

  Log Message:
  -----------
  Use mapped files in CacheStorageDiskStore
https://bugs.webkit.org/show_bug.cgi?id=259371
rdar://problem/112623177

Reviewed by Chris Dumez.

Currently CacheStorageDiskStore reads entire files into dirty memory. When many DOMCache operations
in flight, this can lead to a temporary explosion in NetworkProcess memory usage (in the gigabytes
of footprint).

To fix this issue, we use read-only mapped files in CacheStorageDiskStore instead, as we do with the
regular network cache. This trades dirty footprint for higher vnode usage. But that should be okay
as the number of vnodes consumed by DOMCache should be much lower than the number of vnodes used by
NetworkCache, which is already mmap'ing everything.

I also removed some unnecessary cross-thread copies, as the data we're passing across threads isn't
affined to a particular thread (e.g. no non-atomic ref counts).

* Source/WTF/wtf/FileSystem.h:
(WTF::FileSystemImpl::MappedFileData::toSpan):
(WTF::FileSystemImpl::MappedFileData::create):
* Source/WebKit/NetworkProcess/storage/CacheStorageDiskStore.cpp:
(WebKit::readRecordInfoFromFileData):
(WebKit::CacheStorageDiskStore::readRecordFromFileData):
(WebKit::CacheStorageDiskStore::readAllRecordInfosInternal):
(WebKit::CacheStorageDiskStore::readAllRecordInfos):
(WebKit::CacheStorageDiskStore::readRecordsInternal):
(WebKit::CacheStorageDiskStore::readRecords):
* Source/WebKit/NetworkProcess/storage/CacheStorageDiskStore.h:

Canonical link: https://commits.webkit.org/266199@main